Thermal switch



June 30, 1936. c. J. HARDISON 2,045,948

THERMAL SWITCH Original Filed March 23, 1933 Patented .lune 30, 1936THERMAL SWITCH' Charles J. Hardison, deceased, late of St. Petersburg,Fla., by Betty Hardison, adminstratrix, Jacksonville, Fla.; said CharlesJ. Hardison, assignor of fifty-one per cent to Maxey D. Moody,Jacksonville, Fla.

Original vapplication March 23, 1933, Serial No. 662,401, now Patent No.1,968,828, dated August 7, 1934. ADivided and this 20, 1934, Serial No.131,514

application June 1 claim. (ci. zoo- 122) This invention relates toelectrical switches and more particularly to a thermal switch especiallydesigned for use in connection with automatic oil and temperaturecontrol systems of, the type shown and described in my co-pendingapplication, Serial No. 662,401, filed in the United States Patent OmceMarch 23, 1933, now Patent No. 1,968,828 and of which the presentapplication is a division.

The object of the invention is to provide a switch which willautomatically close a circuit Aand successively illuminate a warninglight and stop the engine of a motor driven conveyance should, for anyreason, the temperature of the fluid in the cooling system become sohigh as to endanger the bearings, cylinder walls and other ,parts ofsaid engine.

A further object of the invention is generally to improve this class ofdevices so as to increase their utility, durability and eillciency.

In the accompanying drawing, forming a part` of this specication, and inwhich similar numerals of reference indicate corresponding parts in allthe figures of the drawing:

Figure 1 is atop plan view of a thermal switch constructed in accordancewith the present invention, the casing or housing of the switch beingshown in section.

Figure 2 is -a vertical sectional view of the same.

Figure 3 is a transverse sectional view taken on the line 3 3 of Figure1.

Figure 4 is` a detail perspective view of the support for the leafspring.

The thermal switch, forming the subject-matter of the present invention,comprises a base 5 of insulating material having a metal plate Iimounted thereon and provided with an upstanding lug 'l on which ismounted, for turning movement, a metallicstud-8 preferably angular incross section and to which is secured one end of a switch arm 9 having aterminal contact member III thereon which coacts with a similar contactmember I I mounted on an upstanding bracket I2 secured to the base,` asshown. The contacts I8 and Il are normally closed and in order to holdthem in closed position a leaf spring I3 is provided, one end ci whichis seated in a 'kerf I4 in the stud 8, while the other end thereof isseated in a slot I5 formed in an upstanding bracket I6 which is securedto the base 5 in any suitable manner, as by a clamping screw I'I. At oneend 'of the base 5 are spaced binding posts I8 and I9 to which areconnected the terminals of a motor circuit, as shown and described in myco-pending application previously referred to. Secured to the bindingpost I8 is a conductor 2| leading to and connected with the stud 8 by aclamping screw 22, the other binding post I9 havins' a conductor 23connected therewith and 4lead- 5 ing to the base of the bracket I2.Disposed at one end of the base 5, opposite the binding posts I8 and I9,is a single binding post 25 connected by a conductor 26 with a warninglight ,(not shown) and to which binding post is secured a l relativelyfine resistance wire 21, the intermediate portion of which is coiled orwrapped around the switch arm 9, as indicated at 28, and is connectedwith-the adjacent end of the conductor 2l by the screw 22. 'I'he purposeof the coil 28 is to heat the switch arm which is of bimetallicconstruction and expand the same as indicated by dotted lines in Figure1 and thus break the' contact between the contact members I 0 and II. soas tointerrupt the motor circuit and automatically stop the engine.

Under normal conditions, the motor circuit to the engine is closed sothat the engine is free to operate in the usual manner. Should thetemperature of the cooling system become too high so as to endanger thebearings and other parts of the engine, a portion of the current willilow through the conductor 2l and thence through the coil 28 so as toheat the switch arm 9. As the switch arm becomes heated it will expandand open the motor circuit and -successively illuminate 'the warninglight and stop the engine, as fully set forth and described in myco-pending application which has matured into patent 1,968,828, issuedAugust '1, 1934. f

It will be `noted that the screw 22 not only serves to connect the Wires2| and 21 to the stud 8, but as the screw extends through the inner endsof the spring I3 and switch arm `9 it also serves to firmly anchor saidspring and .switch arm to the stud.

While the thermal `switch is principally designed for use in connectionwith automatic oil and temperature control systems for motordrivenconveyances, it will, of course, be understood that said switch may beused wherever a `said base and carrying an upstanding pin, a stud 5mounted loosely upon said pin and formed with kerfs spaced from eachother at opposite sides of the pin, .a switcharm having one end seatedin one kerf and having a contact at its other end opposite'thestationary contact, the portion of the arm between the stud and bracketbeing spaced upwardly from the base an appreciable distance, a secondbracket carried by said base. a leaf spring having one end secured inthe second kerf of the stud with its other end secured to the secondbracket, said spring normally holding the switch arm ln position forengagement of its contact with the stationary contact. binding postshaving conductors leading therefrom to the stud and first mentionedbracket, another binding post carried by the base and having a conductorleading therefrom, and a heating coil having its ends secured to thestud and last mentioned conductor, said coil surrounding the switch armand adapted when heated to expand the switch arm and move its contactout of engagementwith the stationary contact and interrupt ilow ofcurrent between the iirst mentioned conduc-

